The class of polymers of carbon monoxide and olefin(s) has been known for some time. Brubaker, U.S. Pat. No. 2,495,286, produced such polymers of relatively low carbon monoxide content in the presence of a free radical initiator, e.g., peroxy compounds. U.K. No. 1,081,304 produced similar polymers of higher carbon monoxide content in the presence of alkylphosphine complexes of palladium compounds as catalyst. Nozaki extended the reaction to produce linear alternating polymers in the presence of arylphosphine complexes of palladium moieties and certain inert solvents. See, for example, U.S. Pat. No. 3,694,412.
More recently, the class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon, now becoming known as polyketones or polyketone polymers, has become of greater interest in part because of the greater availability of the polymers. The more recent processes for the production of such polymers are illustrated by a number of published European Patent Applications including Nos. 121,965, 181,014, 213,671 and 257,663. The processes typically involve a catalyst composition formed from a compound of a Group VIII metal selected from palladium, cobalt or nickel, the anion of a non-hydrohalogenic strong acid and a bidentate ligand of phosphorus, arsenic or antimony. The resulting polymers are relatively high molecular weight materials having established utility as premium thermoplastics in the production of shaped articles such as containers for food and drink produced by well known methods for processing thermoplastic polymers.
In preferred modifications, the catalyst composition employed in the production of the polyketone polymers is formed from a palladium compound, the anion of a non-hydrohalogenic acid having a pKa below about 4, preferably below 2, and a bidentate ligand of phosphorus. The bidentate phosphorus ligands found to be useful are tetraaryldiphosphines of the general type illustrated by 1,3-bis(diphenylphosphino)propane. The particular nature of the phosphorus ligand has considerable importance in the rate at which polymer is produced as well as the molecular weight and other characteristics of the polymer product. The use of a bidentate phosphorus ligand in which each aryl group has an alkoxy substituent on a ring carbon atom ortho to the atom through which the group is attached to phosphorus leads to a high activity catalyst which provides good polyketone product. The advantages of using a catalyst composition based on this ligand must be balanced against an increased degree of reactor fouling obtained when such a catalyst composition is employed. Use of ligands wherein the aryl groups are not alkoxy-substituted gives lower reactor fouling, but also provides a lower catalyst activity.
Methods are available to reduce the reactor fouling. Control of catalyst composition addition is shown to reduce reactor fouling in U.S. Pat. No. 4,914,184. Introduction of particulate matter into the polymerization reactor to reduce fouling is the subject of U.S. Pat. No. 4,940,776. It would be of advantage, however, to provide a catalyst composition which provides a high level of activity but avoids substantial reactor fouling.